HANOVER, N.H. — A comfortable and confident Mitt Romney solidified his front-runner status on Tuesday night in the battle for the Republican presidential nomination, navigating 90 minutes of tough questions on the economy from his rivals and debate moderators.

All eight Republican hopefuls who shared an intimate round table on the debate stage at Dartmouth College clamored to blame Washington for the country’s economic ills. In turn, they pointed fingers at President Obama, the Federal Reserve and the government in general, although they sparred over the details of their plans to grow the economy.

The participants uniformly criticized Obama and official Washington for, in their view, not reviving the economy and for stunting its growth with too many regulations, overreach by the Federal Reserve and inadequate tax relief.

This time, the candidate with whom Romney had to share the spotlight was Herman Cain. The businessman has soared in opinion polls but faced a crush of scrutiny in Tuesday’s debate on an economic plan that he referred to again and again but that his rivals dismissed as overly simplistic and unrealistic. Cain countered that the simplicity of his “9-9-9” plan to gut the federal tax code is its virtue, and he used it to separate himself as a bold outsider in a field of politicians.

During a portion of Tuesday’s Washington Post-Bloomberg debate in which each candidate had a chance to ask another a question, four posed queries to Romney, acknowledging his position as the one to beat.

Meanwhile, Texas Gov. Rick Perry, who was looking to revive his struggling campaign, seized few moments. He stayed silent for long stretches in the debate. When asked how he would fix the nation’s sputtering economy, he said only that he would develop new energy resources. Even when pressed, he offered few specifics.

“What we need to be focused on in this country today is not whether or not we are going to have this policy or that policy,” he said. “What we need to be focused on is how we get Americans working again.”

At another moment, Perry quipped: “Mitt’s had six years to be working on a plan. I’ve been in this for about eight weeks.”

In one exchange, Cain, a former Godfather’s Pizza executive, challenged Romney to name all 59 points in his 160-page economic plan, suggesting that it failed Cain’s test to be “simple, transparent, efficient, fair and neutral” in contrast to Cain’s proposal.

But the former Massachusetts governor did not hesitate to make the case that the complexity of his plan reflects the complexity of the nation’s problems, and that he has the depth of experience, business know-how and ability to deal with those problems.

“I have had the experience in my life of taking on some tough problems,” Romney said. “And I must admit that simple answers are always very helpful but oftentimes inadequate. And in my view, to get this economy going again, we’re going to have to deal with more than just tax policy and just energy policy, even though both of those are part of my plan.”

Not one of the candidates has successfully prosecuted the conservative case against Romney, who on the strength of his political organization and strong debate performances has held steady even though he has been unable to build an insurmountable lead.

Romney, whom conservative voters view warily because of his history of moderate positions on social and fiscal issues, did not help his campaign Tuesday by defending the 2008 bailout of Wall Street banks, which has become a rallying point for the tea party movement and other fiscal conservatives who opposed the government intervention.

“Action had to be taken,” Romney said. “Was it perfect? No.”

He added: “You don’t want to bail out anybody to save a company. The idea of bailing out an institution to protect the shareholders. You do want to make sure that we don’t lose our country or the banking system or American jobs.”

Former Utah governor Jon Huntsman Jr. joined Cain in calling for broad tax reform, while Rep. Michele Bachmann (Minn.) criticized federal regulation of interest rates and the housing industry. Bachmann, former House speaker Newt Gingrich (Ga.) and Rep. Ron Paul (Tex.) took aim at the Federal Reserve — and Fed Chairman Ben S. Bernanke specifically — for regulating currency, interest rates and other aspects of the economy. Former senator Rick Santorum (Pa.) at one point urged that the solution to the nation’s economic problems should revolve around rebuilding the American family

Said Paul: “If you want to understand why we have a problem, you have to understand the Fed. When there are booms and they’re artificial. . . . When you have bubbles, whether it’s the Nasdaq or whether it’s the housing bubbles, they burst.”

Again and again, the Republican contest has been shaped by the debates, which have been filled with moments that have proved pivotal, whether by boosting the candidates’ fortunes or dashing them. A crucial mistake in June by former Minnesota governor Tim Pawlenty crippled his campaign, while Bachmann rode a pair of impressive performances to a victory in the Iowa straw poll. More recently, Perry’s poor showing in a trio of September debates soured voters on his candidacy.

With each debate, the expectations for the primary electorate have shifted, as they have turned their attention to the latest candidate to capture their fancy.

On Tuesday night, that was Cain, after his own debate performances propelled him to the top of opinion polls this month. For him, this was a test of whether he could do what other candidates were unable to do, which is turn his center-stage moment into lasting appeal.

Cain referred repeatedly to his 9-9-9 plan and said he would reduce the federal debt. But the plan he championed became fodder for his rivals.

“I think it’s a catchy phrase,” Huntsman said. “In fact, I thought it was the price of a pizza when I first heard about it.”

Cain shot back: “9-9-9 will pass, and it is not the price of a pizza, because it has been well studied and well developed.”

Bachmann said Cain’s plan wasn’t a jobs plan, but a proposal that would give Congress “a pipeline in a sales tax.”

“When you take the 9-9-9 plan and you turn it upside down, I think the devil is in the details,” she said.

Perry chimed in, too, saying: “I don’t need 9-9-9. We don’t need any plan to pass Congress. We need to get a president of the United States that is committed to passing the types of regulations, pulling the regulations back, freeing this country to go develop the energy industry that we have in this country.”

Later, Perry took aim at Romney’s landmark Massachusetts health-care overhaul, which conservatives have criticized for including an individual mandate much like the one in Obama’s law. Perry asked Romney to address criticisms of the plan, but Romney was ready with a defense.

“I’m proud of the fact that we took on a major problem in my state,” Romney said. “We had a lot of kids without insurance, a lot of adults without insurance. And we said, we don’t want to change anything for the 92 percent of the people that already have insurance.”

He added: “One of the problems with Obamacare is he doesn’t just deal with the people without insurance. He takes over health care for everyone.”

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